(Nonaka Kimihiro): grave accent and @ were the wrong way
-assign keysyms to the special japanese conversion keys (even if this
doesn't help wscons - but things must have names)
"keypad-delete". (This is not completely clean; for me these keys make
up perhaps a "function field", but no "keypad".)
This is the mapping expected by applications.
Proposed by Chris Jones via PR kern/6089 and Dave Sainty.